1. Field of the Invention
This invention relates to a method of reproducing magnetically recorded information by reading out the information from a magnetic recording medium such as a magnetic tape or a magnetic disk by use of a magnetic thin film head, and an apparatus for carrying out the method. This invention particularly relates to a method of reproducing magnetically recorded information by making a light beam impinge upon an inductive type magnetic thin film head and detecting a change in intensity of the light beam reflected by the magnetic thin film head, which is caused by the Kerr effect, thereby detecting the internal magnetization direction in the magnetic thin film head, and an apparatus for carrying out the method.
2. Description of the Prior Art
As the method of recording information in a magnetic recording medium such as a magnetic tape or a magnetic disk and reproducing the information therefrom, various methods have heretofore been known, and various new techniques have been developed by improving the magnetic material and the magnetic head for increasing the recording density. In order to improve the recording density markedly, it is necessary that signal reproduction be achieved at a sufficiently high output even when the movement speed of the magnetic tape or the magnetic disk with respect to the magnetic head is decreased considerably. However, in the case of an inductive type magnetic head, the output naturally decreases to an impracticable level when the tape speed (rotation speed of the magnetic disk) during the signal reproduction is decreased. Further, in the case of the inductive type magnetic head, since the reproduction output level depends on the track width, the extent to which the track density can be increased by decreasing the track width is limited. However, a need exists for further increase of the track density.
Accordingly, instead of the inductive type magnetic head which outputs the speed of change in the internal magnetization of the magnetic head, a magnetic flux response type magnetic head which directly responds to the direction and the degree of magnetization in a magnetic recording medium has recently been proposed. The magnetic flux response type magnetic head is called a magnetic resistive head. In the magnetic flux response type magnetic head, since signal reproduction output does not depend on the tape feed speed or the track width, it is possible to reproduce information recorded at a high density. However, the magnetic flux response type magnetic head is practically disadvantageous in that the signal reproduction output fluctuates greatly with changes in temperature, that the manufacture cost is high since the magnetic head has a special configuration, and that it is not always possible to obtain a magnetic head exhibiting consistent characteristics.
It has also been proposed to make a light beam impinge upon a special magneto-optic recording medium, detect the light beam reflected by the recording medium, and read out the condition of internal magnetization of the recording medium by utilizing the Kerr effect. However, this system is practically disadvantageous in that a special magneto-optic recording medium must be used.